Methods of making electrical circuit boards



4 March 5, 1963 1 A. BAIN,v JR., ETAL 3,079,672

METHODS 0F MAKING ELECTRICAL CIRCUIT BOARDS Filed Aug. 17, 1956 /Z I/'\\!i,/ /4 /3 24 .e l 3 /4 4 .wf/6.2

521 e2 F/@fa --.az l 2//\\\\\\\\\\\\\\\\\\\\\\ l /4 f`/3 /3 W//// A `l2i/kr 2722 i United States Patent Ohce 3,679,672 Fatented lidar. 5, 19533,079,672 METHGDS F MAKEN@ ELETRECAL ClRCUl'l BARDS Lewis A. Bain, Jr.,Hinsdale, and Martin S. Burg, Chicago,

Ill., assignors to Western Electric Company, Incorporated, New York,N.Y., a corporation of New York Filed Aug. 17, 1956, Ser. No. @4,838 2Claims. (Cl. 29--155.5)

This invention relates to the art of printed wiring and moreparticularly to methods of making wired boards.

Objects of the invention are to provide new and improved methods offorming wired dielectric boards.

Another object of the invention is to provide new and improved methodsof forming blocks of plastic material with grooves therein and fillingthe grooves with metal `to provide wired boards.

A further object of the invention is to provide new and improvedmethodsof forming wired boards having apertures and/ or tubular terminalstherein for receiving leads of electrical components and havingconductors embedded in grooves therein and extending betweenpredetermined apertures and/or terminals for electricallyinterconnecting Ithe components.

An apparatus illustrating certain features of one ernbodiment of theinvention may include a die having projecting pins thereon and ribsextending between the pins. The die is pressed into a sheet ofthermoplastic insulating material to perforate the sheet atpredetermined points vand to form grooves therein extending betweenpredetermined perforations. Tubular terminals may be applied to some ofthe pins on the die and pressed through and embedded in the insulatingsheet which is then removed irom the die and electro-conductive materialtilled into the grooves to form conductors extending betweenpredetermined perforations and extending between and electricallyinterconnecting predetermined terminals.

In another embodiment of the invention the die may be used for molding adielectric board wherein tubular terminals are placed on the pins and apastic material is cast around the terminals and over the ribs of thedie and hardened. The board thus formed is then removed from the die andthe grooves therein are filled with electroconductive material toelectrically interconnect predetermined terminals,

A complete understanding of the invention may be obtained from thefollowing detailed description of methods and an apparatus formingspecific embodiments of the invention, when read in conjunction with theappended drawings, in which FIG. 1 is a fragmentary perspectivesectional view of a wired board made by apparatus and methods formingspecific embodiments of the invention;

FIG. 2 is a fragmentary vertical sectional view of an apparatus forpracticing a method forming one embodiment of the invention;

FIG. 3 is a fragmentary vertical sectional view of an apparatus forpracticing a method forming another embodiment of the invention andshowing a wired board made thereby; and

FIG. 4 is a sectional view of an apparatus for practicing a methodforming another embodiment of the invention and disclosing a wired boardmade thereby.

Referring now in detail to the drawings there is shown severalembodiments of apparatus for forming wired dielectric boards ltl(FIG. 1) having grooves i2 formed therein and transverse apertures 13 atthe ends of the grooves and having tubular type terminals or connectors14 at the ends of other grooves l2. Conductors l5 in the grooves 12extending between the aperture t3 and the terminals 14 electricallyinterconnect predetermined terminals and also leads 16 of electricalcomponents 17 inserted into the terminals 14 and into the apertures 13.

The apparatus illustrated in FIG. 2 includes a fixed piaten 2d and amovable platen or die section 21 which is heated by an suitable meansand is movable by means (not shown) relative to the platen 2t).Preformed square wires 22 are spot welded or otherwise secured to theface 23 of the movable platen and heated therewith to form the groovesl2 in the board lil and the wires have upturned ends 24 which form theapertures i3 in the board and which also serves as posts to mount theterminals 14 thereon. Each of the terminals i4 hais a recess formed inone end thereof for receiving the wire 22 to allow the terminal to reston the face 23 of the movable platen 2l. After the terminals E4 havebeen placed on predetermined ones of the ends 2d of the wires 22 a sheet25 of thermoplastic material, such as cellulose acetate, celluloseacetate butyrate, or polyvinyl chloride, having good physical andelectrical insulating properties is placed between the platens 2b and 2land the platen 21 is actuated to press the wires 22 into the lower faceof the sheet 25 and form grooves l2 therein and push the ends 24 of thewires and the terminals la into and completely through the sheet toembed the termina-ls therein.

The platens 2@ and 2i are then separated and the wires 22 with theirupturned ends 24 are withdrawn from the sheet 25 and from the apertures13 and the terminals 14y the latter of which remain in the partiallyformed board l@ at the ends of predetermined grooves 12. The board it)is then inverted and an electrically conductive material is sprayed intothe grooves l2 or an amalgam is'trowelled into the grooves and hardenedto form the conductors l5 which are securely held in the square groovesi2 and extend between predetermined apertures i3 and terminals 14 andelectrically interconnect predetermined terminals. The amalgam may beany one of a number of well known amalgame, such as silver amalgam,which expand upon solidication to anchor the conductors formed therebyin the grooves. A mask is used to cover the ungrooved portions of theface of the board when the metal is sprayed into the grooves.

ln another embodiment of the invention (FiG. 3) preformed wires 122 aretemporarily fastened to the lower movable platen i21 by clips or othersuitable fasteners in a predetermined pattern with the end portions 124of the wires projecting upwardly. A sheet 125 of thermoplastic materialis disposed between the platen 121 and the upper fixed platen i2@ andthe lower platen is actuated to press the wires 22 into the plasticsheet 125. The platen 121 is then withdrawn, leaving the wires 1.22embedded in the board itl with the intermediate portions of the wireslilling the grooves l2 in the board and forming the conductors l5, andthe ends 21.24 of the wires extending through the board and projectingfrom the upper side thereof to form mounting or terminal posts to whichelectrical components may be connected.

in the embodiment shown in FlG. 4 a die 221 is provided with side wallsaround its periphery to form an open mold cavity. Preformed square wires222 are welded or otherwise secured to the upper iiat face of the die221 in a predetermined pattern with the ends 224 of the wires extendingupwardly therefrom in predetermined positions. Tubular terminals 14 arethen placed on the ends 224 o the wires and a casting resin such as apolyester or an epoxy resin or a suitable thermoplastic material in aliquid or semidiquid state is poured into the mold cavity to a levelsubstantially iush with the upper ends of the terminals ld and hardenedaround the terminals to form the board lli. After hardening, the boardl@ with the terminals 14 embedded therein is withdrawn from the die 222iand the grooves 12 formed in the board are lled with amalgam or otherlow-melting metals to form Vthe conductors 15 interconnectingpredetermined terminals.

The above-described methods and apparatus serve to quickly andinexpensively form Wired boards from the thermoplastic or thermosettingmaterial to form low cost wired boards in which conductors are embeddedin one face thereof for interconnecting `velectrical components placedincontact therewith and in which apertures or tubular terminals areprovided` at the ends of predetermined ones of the conductors f orreceiving leads of the electrical components and electrically connectingthem to the conductors 4 i It is to he understood that theabove-described ar'- rangements are simply illustrative of theapplication of the principles of this invention. Numerous otherarrangements may be readily d evised bythoseskilled in the `rart which`will embody the'principl'e-s of the invention and vr fall withinthespirit and scope thereof.

What'is claimed is: Y p n 1. Amethod of'making electrical circuit boardswhich jeornprises forming wires intopredeterrnined shapes with the endportions of predetermined length disposedparall"lel to one another inthesame direction transversely of the intermediate portions ofthe Wires,heating the Wires 'and movin-g the wires parallel to the end portionsthereof in a direction toward andI perpendicular to athermoplas'tieboard of less thickness than the length of the 'endportions of the wires "to force the end portions of :the 30 iviresl'through the board to forni` terminal posts projecting'from 'th'eb'oardand to j'e'r'x'rbed the'intermediate portions of the wires in the'board.l y

y 2. A method of embedding Ulshaped Wires in ya at ofdet'achablyclipping the bights of the U-shped wires to a'rst'r'novahle platen withthe legs of the wires perpendicularly projecting from the surface of thefirst platen, supporting the insulating board over the ends of the legsof the wires, heating the iirst platen and the wires to a degreesuicient to place the insulating board in a softened state, advancingthe platen to advance the insulating board against a second fixed platenhaving spaced holes to accommodate the heated legs and to force the endportions of the Wires through the insulating board to form terminalposts projecting therefrom, and then moving the first platen from thesecond platen to'detach th'ewires from theclips to leave the bightsfan'dportions of the legs embedded in the-insulating board.

` References Cited in the file of this patent 'UNITED STATES 'PATENTS iiinlin -RES rnntdleireuir Techniques, 4.tiranni Bure-auferstand- 'rdsCinestar' 46a-Nov. -1 5, A1947.

1. A METHOD OF MAKING ELECTRICAL CIRCUIT BOARDS WHICH COMPRISES FORMINGWIRES INTO PREDETERMINED SHAPES WITH THE END PORTIONS OF PREDETERMINEDLENGTH DISPOSED PARALLEL TO ONE ANOTHER IN THE SAME DIRECTIONTRANSVERSELY OF THE INTERMEDIATE PORTIONS OF THE WIRES, HEATING THEWIRES AND MOVING THE WIRES PARALLEL TO THE END PORTIONS THEREOF IN ADIRECTION TOWARD AND PERPENDICULAR TO A THERMOPLASTIC BOARD OF LESSTHICKNESS THAN THE LENGTH OF THE END PORTIONS OF THE WIRES TO FORCE THEEND PORTIONS OF THE WIRES THROUGH THE BOARD TO FORM TERMINAL POSTSPROJECTING FROM THE BOARD AND TO EMBED THE INTERMEDIATE PORTIONS OF THEWIRES IN THE BOARD.